The present invention relates to a control circuit and more specifically to a control circuit for a cool/heat pump room air conditioner.
Room air conditioners are well known and are of the type that generally fit in a window or in a sleeved opening formed through the wall of a room. Most such room air conditioners utilize a fluid refrigerant which is caused to alternately expand and condense to provide the desired cooling effect inside the room and to expel heat outside of the room. The refrigerant flows through a system which includes an evaporator where liquid refrigerant is permitted to evaporate thereby cooling a coil surface of the evaporator in order to extract heat from air within the room. A fan is used to cause room air to flow over the coil of the evaporator. The refrigerant then flows to the compressor where it is returned to a high pressure gas state. The refrigerant then flows to a condenser, generally positioned outside of the room wherein the refrigerant vapor condenses and gives off heat. Generally a fan is also provided on the condenser side to provide a flow of outside air over the condenser coil to remove heat therefrom. Refrigerant then flows to an expansion device where it is turned to a low pressure liquid state before flowing again to the evaporator.
It is known that by reversing the flow through the system, the air conditioner can act as a heat pump to draw heat from exterior of the room and to provide that heat to the interior of the room. In such an arrangement the refrigerant flow is reversed and what was the evaporator now acts as the condenser to release heat and what was the condenser now acts as the evaporator to absorb heat from the surrounding air.
Control systems for room air conditioners are well known and in such control circuits generally include a switch for powering a compressor motor and a fan motor as well as sometimes controlling other components.
Generally the type of motors utilized in such air conditioners have both a main winding and an auxiliary winding with capacitors in series with the auxiliary winding. Control circuits which have been provided for such air conditioning units and motors are disclosed in the following U.S. Pat. No(s). 2,242,370; 2,782,351; 3,045,159; 3,146,387; 3,385,077; and 3,852,648. Such circuits are limited to air conditioner units, however, and do not appear to provide the necessary controls for heat pump operation.
The above listed patents describe various types of control circuits and including circuits in which a single, dual rated capacitor is used in series with each of the two motor auxiliary windings.
Applicant has determined that in the application where such a room air conditioner is also being utilized as a heat pump, additional considerations arise over those necessary for controlling a room air conditioner, including the need to provide a de-icing circuit for the evaporator when the unit is being operated as a heat pump and, during such operation, the refrigerant flow must be reversed so as to provide a warming to the evaporator coil. Since the heat pump is generally being used to heat the interior space, it would be detrimental for the interior fan to run during the de-icing operation because during the de-icing operation the interior coil is acting as an evaporator and would thus result in cold air being blown from the evaporator coils. Therefore, it would be an improvement in the art for there to be provided a control circuit for a cool/heat pump room air conditioner which will control the various components with minimum number of parts, yet provide the desired heating and cooling and prevent undesired cooling effect within the room during a de-icing operation.